1. Field of the Invention
The invention relates to a variable focal length lens panel and fabricating the same wherein the variable focal length lens panel can be used as a lens, for example, for an optical pickup used both in a compact disc (CD) and a digital video disc (DVD) in an optical disc drive.
2. Description of the Related Art
There has been conventionally developed a liquid crystal lens capable of varying a focal length by an applied voltage, which is, for example, disclosed in Japanese Patent Laid-Open Publication No. H4-240817.
As shown in FIG. 9, a variable focal length lens disclosed in this publication has such structure that 320.times.220 pixels are arranged in a lattice shape by transparent electrodes in a display area 41 which is recorded as a phase type Fresnel zone plate 42 of a liquid crystal space optical modulator 40, and ECB (electrically controlled birefringence) mode liquid crystal is sealed in the display area 41.
The liquid crystal space optional modulator 40 has a light wave modulation characteristic such that when a voltage is applied to the transparent electrodes, laser beams undergo continuous phase modulation in the range of 0 to 2.pi.. At the time of such phase variation, by applying a voltage signal Vs that effects every pixel with a phase modulation corresponding to the spatial coordinates thereof, laser beams 43 which incident on the liquid crystal spatial optional modulator 40 undergo a phase modulation by respective pixels, and concentrated on a focal point Fa on the optical axis as shown in FIG. 10. Further, if a different voltage signal Vs is applied, the light-concentrating position of the laser beams 43 can be moved to a point Fb on the optical axis.
However, the publication set forth above merely discloses a theoretical construction, it does not disclose concrete shapes and constructions of the respective transparent electrodes serving as the variable focal length lens and does not disclose the explanation of materials in the embodiment, hence it is not practicable.
A liquid crystal lens is also disclosed in Japanese patent Laid-Open Publication No. H3-2840. Briefly explaining this liquid crystal lens, it comprises a liquid crystal, a control electrode for applying a voltage to the liquid crystal, and a fixed electrode, wherein the control electrode is composed of circular or concentric ring-shaped transparent electrode bands 47 and insulating bands 46 for insulating between the transparent electrode bands 47, as shown in FIG. 11. Respective transparent electrode bands 47 are independently wired.
Polarizers may be disposed at both sides of the liquid crystal panel. If polarizers are not disposed, when a voltage is applied to the transparent electrode bands 47, the liquid crystal panel turns the direction of polarization of incident light 90.degree. while the incident light passes thereby in the areas where the transparent electrode bands exist, and permits incident light to pass through as it is in the other areas.
Accordingly, light beams which emerge out from the liquid crystal lens can form images independently without interfering with one another on the same point, wherein the focal length thereof is varied by a voltage applied to the transparent electrode bands 47.
However, practicable concrete shapes and materials are not disclosed, and a method of fabricating the liquid crystal lens is indistinct, and hence the liquid crystal lens shown in this publication has not been put into operation.
As mentioned above, the conventionally proposed variable focal length lenses are theoretical or principled and do not specify practicable concrete shapes and constructions, and methods of fabricating the same are not disclosed, so that they have not been put to practical use.